Encoding and decoding method for short-range communication using an acoustic communication channel

ABSTRACT

Encoding and decoding methods are provided. An information object is encoded according to a preset encoding scheme. A preset set of bits is selected from the encoded information object and the selected set of bits is output as a sample. A control packet including information on a sample number is generated. The sample is assembled with the control packet. The sample is modulated into a sound signal according to a preset scheme. An input sound signal is demodulated according to the preset scheme. Sample bits and control packet bits containing information of the sample are separated from each other in demodulated received bits. Address information corresponding to each bit of the sample is generated according to the control packet. A soft decision of the sample bits is summed for each piece of the generated address information. A sample decoding of the summed soft decision of the sample bits is performed.

PRIORITY

This application is a Continuation Application of U.S. application Ser.No. 12/782,520, filed on May 18, 2010, now issued as U.S. Pat. No.8,737,435, which claims priority to an application filed with theRussian Intellectual Property Office on May 18, 2009 and assigned SerialNo. RU2009119776 and the Korean Intellectual Property Office on Apr. 9,2010 and assigned Serial No. 10-2010-0032589, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to encoding and decoding schemesand data transmission and reception devices for wireless communicationsystems, and more particularly to facilitating the systems ofshort-range communication between stationary or mobile devices andmobile (including portable) devices, using an acoustic communicationchannel for data transfer over short distances.

2. Description of the Related Art

Encoding and data transfer apparatuses, used for different types ofcommunication channels are widely known, and include a disassembler fordisassembling an information object into data packets, wherein eachpacket is conveyed in a certain sequence to the error-correcting codingunit, the interleaver, the unit of control data addition.

The encoded packets are conveyed to the modulator, synchronizationsequence addition unit and further to the encoder output fortransmission through the communication channel. High noise immunity ofdata transfer is usually achieved by means of encoding with a high levelof redundancy, enabling transmission of the objects with an increasedprobability of error-free reception in the communication channel withconsiderable interference, but causing a significant decrease in theobject transmission speed on the other hand.

There are systems of information objects transfer by means of audibletones, including transceiver T (including a transmission apparatus) bothin the receiving and transmitting section. Nonetheless, during thetransmission, transceiver T1 includes a disassembler for disassemblingan information object into data packets, each of which is conveyed tothe encoder and the interleaver in a certain consequence. Furthermore,the transceiver T1 includes a modulator, where the converted packets aremodulated by the audio signals and conveyed to transceiver 2 through thedigital-to-analog converter and the loudspeaker. While reception at theanalog-to-digital converter of transceiver 2, the audio signal receivedthrough the microphone is digitized, then is transferred successively tothe synchronization unit, demodulator, deinterleaver, decoder, datarestorer. At the same time, each incoming data packet is restored, thetransmitted object is gradually received and its quality/integrity isdetermined. In case of losses transceiver T2 transmits a correspondingsignal to transceiver T1, after conveying of the said signal, the newparameters of transmission through the acoustic communication channelare established (for example, power of the acoustic tone is increased)and the object is repeatedly transferred to transceiver T2. A drawbackof such systems is the complexity of apparatuses in receiving andtransmitting section, since a feedback mechanism is obligatory betweenthe apparatuses in the receiving and transmitting sections (each of themmust contain transceiver); slow response to the changing noise situationand, as a consequence, low rate of information objects transmission.

There also exist acoustic transmission systems, where the informationobject transmission speed is constant, does not take into accountinterference (acoustic) or environment (degree of noisiness of acousticchannel). Also, there is a feedback communication channel used foradjusting modulation type or speed of the error-correcting code.

The most relevant is a system of the acoustic data transmission withoutfeedback, in which the transmission apparatus encodes the informationobject en bloc and cyclically repeats its transmission. The receivingapparatus in the receiving mode makes attempts to receive the encodedobject until its error-free reception is achieved.

The drawback of the system is its inefficiency. In the case of at leastone error during reception, repeated transmission is expected and thetransmitted code and the audible tone parameters remain unchanged. Thus,during objects transmission, especially of a large amount of data, thepossibility of erroneous reception increases drastically, and thetransmission speed decreases and can not be optimal for the arbitrarysignal to noise ratio in the communication channel. Therefore, aninformation object transmission either with high noise immunity (a lotof redundant (checking) data during object encoding) is necessary sothat the error-free reception can be provided by means of one-tworepetitions, which affects the speed, or increased transmission speed,in which case, noise increase in the communication channel adverselyaffects the noise immunity and the object may not be received at all.

SUMMARY OF THE INVENTION

The present invention relates to encoding and information transmissiondevices for wireless communication systems.

An object of the present invention is the creation of an encoder,transmission apparatus, and an information object transmission system,enabling the considerable increase of transmission speed of informationobjects compared to existing devices and systems, using an optimalvolume of the transmitted information and optimal redundancy of theerror-correcting code in the chosen communication channel. Creation ofsuch apparatuses and the system will enable transmission of theinformation objects of any size, which will increase their scope ofapplication considerably.

According to an aspect of the present invention, an encoding method isprovided. An input information object is encoded according to a presetencoding scheme. A preset set of bits is selected from the encoded inputinformation object and the selected preset set of bits is output as asample. A control packet including information on a sample number foridentifying the sample is generated. The sample is assembled with thecontrol packet. The assembled sample is modulated into a sound signalaccording to a preset scheme.

According to another aspect of the present invention, a decoding methodis provided. An input sound signal is demodulated according to a presetmodulation scheme. Sample bits and control packet bits containinginformation of a corresponding sample are separated from each other indemodulated received bits. Address information corresponding to each bitof the corresponding sample is generated according to a control packet.A soft decision of the sample bits is summed for each piece of thegenerated address information. A sample decoding of the summed softdecision of the sample bits is performed.

According to a further aspect of the present invention, an encoding anddecoding method is provided. An input information object is encodedaccording to a preset encoding scheme. A preset set of bits is selectedfrom the encoded input information object and the selected set of bitsis output as a sample. A control packet including information on asample number for identifying the sample is generated. The sample isassembled with the control packet. The assembled sample is modulatedinto a sound signal according to a preset scheme. An input sound signalis demodulated according to the preset scheme. Sample bits and controlpacket bits containing information of the sample are separated from eachother in demodulated received bits. Address information corresponding toeach bit of the sample is generated according to the control packet. Asoft decision of the sample bits is summed for each piece of thegenerated address information. A sample decoding of the summed softdecision of the sample bits is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of the transmission apparatus according to thepresent invention;

FIGS. 2A and 2B illustrates an example of a distribution of theamplitude spectrum of the transmitted signal in the case of the uniformspectrum of acoustic noises, and in the case of the existence ofacoustic noise, focused in the narrow band, according to the presentinvention;

FIG. 3 is a block diagram of the receiving apparatus according to thepresent invention; and

FIG. 4 illustrates the disclosed system parameters compared to theconventional method (in the form of dependence of time, required forobject transmission, on signal to noise ratio in the communicationchannel).

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are described in detail withreference to the accompanying drawings. The same or similar componentsmay be designated by the same or similar reference numerals althoughthey are illustrated in different drawings. Detailed descriptions ofconstructions or processes known in the art may be omitted to avoidobscuring the subject matter of the present invention.

The transmission apparatus of the system, presented on FIG. 1, includesan encoder 1, the first input (In1) and the second input (In2) of whichare informational. Digital to analogue converter (DAC 102) andloudspeaker 103 are successively connected to the output of the encoder.To the additional input (ad. Input) of the encoder, intended forcommunication channel diagnostics, through analog-to-digital converterADC 104 of the transmission apparatus encoder, the microphone (M1) ofthe transmission apparatus 105 is connected.

The encoder 1 includes a precoder 10 for encoding an input informationobject according to a preset encoding scheme and storing the informationobject in a precoder buffer; a sample number/address generation unit 12for generating a sample number of each sample and an address, whichcorresponds to each bit of each sample and the address of the precoderbuffer; a multiplexer 110 for selecting a bit of each precoder buffercorresponding to the address generated by the sample number/addressgeneration module 12; a sampling buffer 111 for storing a bit of eachsample output from the multiplexer 110; a control packet generationmodule 14 for generating a control packet including information on thesample number generated by the sample number/address generation module12; a packet assembling unit 112 for assembling the sample stored in thesampling buffer 111 with the control packet generated by the controldata generation module 14; and a modulation module 16 for modulating thepacket output from the packet assembling unit 112 into a sound signalaccording to a preset scheme.

Further, the encoder 1 may further include a spectrum calculation module18 for receiving information on an exterior sound communication channeland calculating a sound spectrum based on the received soundcommunication channel, and the modulation module 16 may further includea configuration for compensating for the spectrum of the sound signalbased on the information provided by the spectrum calculation module 18.

The sample number/address generation module 12 may include a samplenumber generator 115 and an encoder address generator 116, and thecontrol packet generation module 14 may include a control datageneration unit 113 and a control data encoder 114. Further, themodulation module 16 may include a spectrum correction unit 117, amodulator 118, and a synchronization sequence addition unit 119, and thespectrum calculation module 18 may include a communication channelanalyzer 120 and a spectrum estimator 121.

The configuration and operation of the encoder 1 and the transmissionapparatus as described will be described in more detail hereinafter.

In the embodiment shown in FIG. 1, the encoder 1 includes theapparatuses successively connected and forming the precoder 10: acontainer compacting unit (CCU) 106 of the input data, the inputs ofwhich being at the same time the first input (In1) and the second input(In2) of the precoder, the encoder and the transmission apparatus, arepeating/interleaving unit (RIU) 107, a convolution encoder (CE) 108,and a precoder buffer (PB) 109. Inputs/Outputs of the precoder buffer109 are inputs/outputs of the precoder 10 and are coupled to therespective inputs/outputs of multiplexer 110. The multiplexer output isconnected through sampling buffer (SB) 111 to the first input (In1) ofpacket assembly unit (PAU) 112. In that way the channel of preparationof the primary encoder data is formed (primary channel).

The second input (In2) of the encoder 1 is connected to the first input(In1) of control data generation unit (CDSU) 113 and further—through thecontrol data encoder (CDE) 114—to the second input (In2) of the packetassembly unit (PAU) 114. At the same time, the channel of the encodercontrol data preparation is formed (control channel).

The output of the sample number generator (SNG) 115 is coupled to thesecond input (In2) of the control data generation unit (CDSU), as wellas with the multiplexer through the encoder address generator (EAG) 116,also connected to the second input (In2) of the encoder. The secondinput (In2) of the encoder 1 may be coupled to the additional input ofthe repeating/interleaving unit 107.

The output of the packet assembly unit (PAU) 112 is connected to theoutput of the encoder through the successively connected spectrumcorrection unit 117, modulator 118, and synchronization sequenceaddition unit (SSAU) 119.

The additional input (AddIn) of the encoder 1 is connected to theadditional input of the spectrum correction unit 117 through thesuccessively connected communication channel analyzer (CCA) 120 andspectrum estimator (SE) 121 for calculation of the optimal amplitudespectrum of the transferred signal.

The other additional inputs of the encoder 1 and/or transmissionapparatus may be envisaged (not shown on FIG. 1). For example, a startinput for signaling to specific encoder units of the necessity totransfer input data, as well as an input of the alternativecommunication channel, intended also for commanding to the encoder ofthe input data transfer termination.

The transmission apparatus circuit is configured to enable power supplyof all circuit elements requiring it.

The transmitting section of the system, including the transmissionapparatus, functions as follows.

The transmission apparatus is switched on when the encoder 1, thedigital-to-analog converter 102, the analog-to-digital converter 104,the loudspeaker 103, and the microphone 105 are energized and in astandby mode.

On the preliminary stage of encoding during the input data entry to thefirst input (In1) of the transmitter (information object IO—file,message, application etc.), and to the second input (In2) of thetransmitter—data of the IO size, coming simultaneously to encoderaddress generator 116 and to the first input (In1) of control datageneration unit 113, in container compacting unit 106 an informationobject is packed into a standard container. For this purpose, a headerlabel is added to the information object and a bite set for integritychecking (for example, check sum, CRC, Hash-code etc.)

Furthermore, in the container compacting unit 106, the container may beencoded by means of error-correcting code (e.g. Reed-Solomon code). Thecontainer (from the container compacting unit (CCU) and a size ofinformation object (IO) (from the CCU or from the second input (In2) ofthe encoder) are conveyed to the repeating/interleaving unit 107, wherethe data bits of the container are repeated a definite number of timesand mixed. Pseudorandom function of such rearrangement depends on theinformation object size.

Thereafter, a convolution code encoding is carried out in theconvolution encoder 108. It is known that formation of encoded bits inthe indicated manner (i.e. repeating with interleaving followed byconvolution encoding) enables the achievement of a high noise-immunityof the code, in the case of iterative decoding at the receiving section(see example [3]). However, in the suggested technical solutions encodedin this manner, the information object (data block for transmission) isnot directly transmitted to the modulator and in the communicationchannel. It is transferred to precoder buffer 109 from the convolutionencoder.

The data block for transmission is stored in the precoder buffer for themain stage of encoding. Preliminary stage is carried out only oncebefore beginning of transfer through the communication channel (in thisembodiment—acoustic), leaving the precoder buffer content unchanged inthe case of necessity of further adjustment of the transmissionproperties according to the changing communication channel.

It should be kept in mind that the precoder in the other embodiments ofthe suggested technical decisions may be formed by any known method. Inwhich case the error-correcting code with arbitrary redundancy may beused.

Then, the basic stage of the encoding is carried out. In the switched ontransmission apparatus, start up of sample number generator 115 iscarried out by any method known (namely, by the command from the startinput or repeating/interleaving unit). The sample number generator isgenerating identification numbers with a definite periodicity (random orsuccessive values) for sampling of bits from the precoder buffer andconveys them to the encoder address generator and to the second input(In2) of control data generation unit 113.

When the data from the second input (In2) of the encoder 1 enters theencoder address generator 116 (which means information object entry intoencoder 1), the received value of the sample number from the samplenumber generator 115 initializes the pseudorandom encoder addressgenerator 116, forming a set of k addresses, which are successivelyconveyed to multiplexer 110. In accordance with a set of addresses viainputs/outputs of the multiplexer 110, pseudorandom sampling of k bitsfrom the precoder buffer 109 is carried out and they are stored in thesampling buffer 111. The encoder address generator 116 generates knumber of addresses within the range of 1 to N, where N is a number ofbits in the precoder buffer 109 for the predetermined size of thecontainer. Further, k is properly determined according to the value ofthe second input (In2) of the encoder, i.e. according to the informationobject size.

In this case, addresses may recur once or more times both in one set andduring pseudorandom generation of the following address sets. In thepreferred variant pseudorandom function of the encoder address generatoris assigned so that the recurrence interval of generated addresses ismaximal. At the same time it should be noted that the samples repetitiondoes not result in considerable speed and noise immunity decrease of thetransmission system under consideration providing optimal decoding inthe receiving apparatus, presented on FIG. 3.

Sampling bits from the sampling buffer are conveyed to the first input(In1) of packet assembly unit 112, without application of additionalerror-correcting coding. Thus preparation for information objectsfragments transfer is finalized in so called “primary channel”.

At the moment of information entry from the second input (In2) of theencoder into the control data generation unit through the first input(In1), value of the sample number entering at the second input (In2) ofthe control data generation unit, from the sample number generator,initializes operation of the control data generation unit, whichassembles control data, containing object size and/or container size (inconsideration of the container compacting unit operation), sampleidentification number, and other auxiliary information as well. Controldata in the control data encoder 114 is coded by the error-correctingcode and the special checking symbols are added for checking the controlpacket integrity (e.g. its CRC, check sum etc.), receiving controlpacket, which is transmitted to the second input (In2) of the packetassembly unit. Thus, simultaneously with each sample formation in the“primary channel” corresponding to it control packet is formed in socalled “control channel”.

As a rule, codification in the control channel is carried out by a highredundancy code and consequently, high noise immunity, so that thecontrol channel could be received in severe noise and interferenceconditions in the communication channel. At the same time, the controlchannel contains only a small amount of information compared to theinformation volume in the primary channel, that is why cumulativeredundancy conditioned by the control channel presence is comparativelysmall.

Organization of such a two-channel codification (redundancy in theprimary channel is small compared to the control channel redundancy)provides the possibility of considerable increase of information objecttransfer speed, of the large objects as well (the lower is the dataredundancy of the primary channel, the higher is the information objecttransfer speed by means of pseudorandom samples). By the same degree ofnoise immunity in the primary and control channels, information objecttransfer speed also increases considerably due to high probability ofiterative reception of separate samples and respectively, successfulrestoration of the information object.

The main channel and the control channel may have different securitymechanisms and different physical formats. The control channel carriesinformation, which enables decoding of the main channel and includes thelength of an information object transmitted through the main channel andthe sample number of a current sample. The sample number servers as aspecific identifier for notifying a receiving apparatus of the dataarrangement of the main channel.

In general, the encoding operation of the main channel includes twostages. In the first stage, the original information object is repeatedseveral times and then interleaved. Then, the resultant object may bedecoded by using, for example, convolution codes having a ratio of1/(R+1) (that is, R parity bits are generated for each original bit ofthe information object), and all the bits decoded in the convolutionencoder 108 are stored in the precoder buffer. In the second stage,during each packet generation interval, a set of preset bits areselected from the bits stored in the precoder buffer 109 according tothe address generated by the encoder address generator 116. Thereafter,these bits are transmitted together with the control channel data.

Control packet bits and sample bits form optimal size data packets. Theoptimal packet size is chosen based on two considerations: on the onehand, as it was noted, volume of the data transferred through theprimary channel must be considerably larger than the data volume in thecontrol channel, so that the high redundancy of the code in the controlchannel does not considerably affect cumulative effectiveness of thetransmission system; on the other hand, in many applications the packettransmission time must be comparatively short (e.g. 1 sec.) since theexcessively long packet may result in undesirable delay during objectsreception, especially small ones.

The data packet is modulated in the packet assembly unit by means of oneor several kinds of modulation (such as BPSK, QPSK, n-QAM), addingspecial pilot symbols for simplifying evaluation and channelequalization procedure in the receiving apparatus. In the system underconsideration broadband modulation with one or multiple carriers may beused (e.g., OFDM, CDMA etc.). In order to reduce perceptibility of theaudible tone to the user, at the same time preserving an average powerand wideband properties of the tone, tone spectrum is corrected in thespectrum corrector 117 prior to transmission to modulator 118, in whichcapacity a filter can be used for example. Spectrum correction may beperformed adaptively.

Such correction is possible if the apparatus includes the microphone(M1) 105 and the analog-to-digital converter 104. In this case, incommunication channel analyzer (CCA) 120 audible tones are analyzed withdefinite periodicity, the said tones conveyed from the microphone (M1)105 through the analog-to-digital converter (ADC1) 104, evaluating thelevel and spectral composition of the acoustic noise in thecommunication channel. In which case in the given system embodiment bythe acoustic noise all the audible tones are meant (speech, music,audible tone of notification etc.), with exception of the signal,emitted by the transmission apparatus itself. Then, in compliance with apsycho-acoustic model of acoustic perception, implemented in thespectrum estimator (SE) 121, calculation of the optimal signal spectrumis carried out, by which the power of the signal is maximal provided itsunchanged acoustic perceptibility.

In particular, in the spectrum estimator (SE) frequency concealmenteffect is applied, which is illustrated in FIGS. 2A and 2B, where thepreferable signal spectrums are indicated with the firm line in thecommunication channels with acoustic noise (dash line). Thus, in casethe acoustic noise level is close to the uniform (FIG. 2A), distributionof the amplitude spectrum is inversely proportional to the averagesensitivity of the human ear to the noise signal (for example, suchsensitivity characteristic is determined in the standard ITU-R 468).

In case of severe acoustic interference with expressed peaks in thecertain frequencies, optimal distribution will be determined by earsensitivity to noise signals taking into account the frequencyconcealment effect. Such distribution example is given on FIG. 2B. Asevere unwanted audible tone is masking the signal components, locatedon the neighboring frequency intervals, that is why on the adjacentfrequencies the intensiveness of the transferred signal may be increasedwithout subjective increase of acoustic volume of the signaltransferred.

From the spectrum estimator, estimated data is transferred to thespectrum corrector, where the spectrum correction of the signal iscarried out in accordance with the changing communication channel foreach data packet, which still further increases possibility oferror-free data reception by the receiving apparatus (hence increasingtransmission speed as well), and leaving transmitter signal barelynoticeable to the user.

Further, in the modulator 118, the corrected symbols are modulated,obtaining the information signal, and in the synchronization sequenceaddition unit 119 synchronous signals are added in the time domain tothe data signal for simplification of the synchronization and channelalignment procedure in the receiving apparatus. Obtained in this waytransmission signal is conveyed to digital-to-analog converter 102 andLoudspeaker 103—to the communication channel.

Thus pseudorandom samples from the information object are continuouslytransferred to the communication channel.

The receiving apparatus of the system, presented on FIG. 3, includes adecoder 2, to the input (In) of which a microphone (M2) 203 of thereceiving apparatus is connected through an analog-to-digital converter(ADC2) 202 of the receiving apparatus.

The decoder 2 includes a demodulation module 20 for demodulating aninput sound signal according to a preset modulation scheme; a firstdemultiplexer 207 for deciding a soft value of each reception bit outputfrom the demodulation module 20 and separating sample bits and controlpacket bits containing information of a corresponding sample from eachother; an address generation module 22 for generating an addresscorresponding to each bit of the corresponding sample; a seconddemultiplexer 208 for receiving the soft decision of the sample bits anddemultiplexing and outputting the soft decision according to the addressinformation generated by the address generation module 22; a summationunit for summing the soft decision for each output of the seconddemultiplexer 208; a storage buffer 210 for storing the summed softdecisions from the summation unit 209; and a decoding module 24 fordecoding the samples stored in the storage buffer 210.

The demodulation module 20 includes a synchronizer 204, a demodulator205, and a communication channel estimation/compensation unit 206, andthe address generation module 22 includes a control channel decoder 211and a decoder address generator 212. Further, the decoding module 24includes an iterative decoder 213, a data integrity check unit 214, anda container unpacking/restoring unit 215.

Hereinafter, the configuration and operation of the decoder 2 and thereceiving apparatus according to the present invention will be describedin more detail.

The decoder 2 includes the decoder input synchronizer 204, demodulator205, communication channel evaluation/compensation unit (CCECU) 206 andthe first demultiplexer (DM1) 207, which are successively connected toeach other.

The first output (Out1) of first demultiplexer (DM1) 207 is coupled tothe first input (Input1) of the second demultiplexer (DM2) 208, outputsof which are connected through the respective summation units (Σ) 209 tothe corresponding inputs of storage buffer (SB) 210. Number of summationunits corresponds to the number of bits in the precoder buffer of theencoder.

The second output (Out2) of first demultiplexer (DM1) 207 is connectedto control channel decoder 211, the first and the second outputs ofwhich are connected to the respective inputs of decoder addressgenerator 212, the output of which is coupled to the second input (In2)of the second demultiplexer (DM2) 208.

The storage buffer 210 is coupled to the output of the decoder, beingthe data output (Out) of the receiving apparatus, through thesuccessively connected the iterative decoder (ID) 213, the dataintegrity checking unit (DICU) 214, and the unpacking/restoring unit215. At the same time, the additional output of the data integritychecking unit is connected to the additional input of the iterativedecoder, as well as to the additional output of the decoder, being theadditional output (AddOut) of the receiving apparatus.

The receiving apparatus circuit is configured to enable the respectivepower supply to all circuit elements, requiring the said supply.

The receiving section of the system, including the receiving apparatus,operates in the following way:

The receiving apparatus is switched on, when the decoder 2, theanalog-to-digital converter (ADC2) 202, and the microphone (M2) 203 areenergized and are in standby mode.

The signal from the communication channel through the microphone (M2)203 is conveyed to the analog-to-digital converter (ADC2) 202, where itis digitized and transferred to the input of the decoder. Insynchronizer 204, after detection of the transmission signal by thesynchronous signal, boundaries of the signal are restored and correctiveadjustment of the sampling frequency is carried out, the incoming signalis received. Hereafter the received signal is conveyed to demodulator205 with one or multiple carriers, implemented correspondingly tomodulator 118 (on the basis of filter bank or fast Fouriertransformation (see for example [1])). In the communication channelevaluation/compensation unit (CCECU) 206, using pilot symbols,evaluation of the communication channel and the noise components iscarried out and a distortion spectrum is evaluated adaptively. In thefirst demultiplexer 207, “soft” values of the received bits aredetermined, separating sample bits for the “primary” channel and controlpacket bits for the “control” receiving channel.

The “soft” decisions of the control packet are conveyed to controlchannel decoder 211, designed in compliance with the control dataencoder 114. In case of the control packet successful decoding,container size data through the first output of the control channeldecoder and a sample identification number through the second output ofthe control channel decoder is transferred to the respective inputs ofpseudorandom decoder address generator 212, analogous to the encoderaddress generator of the transmission apparatus. At the same time, bitaddresses are generated in the decoder address generator, correspondingto the addresses of the precoder buffer of the transmission apparatusencoder.

The “soft” decisions, corresponding to the sample, are demultiplexed bythe second demultiplexer (DM2) 208 in accordance with addressinformation, generated by the decoder address generator. Hereafter,“soft” decisions with each received sample, are gradually cumulated inthe corresponding summation unit (Σ) 209 (each storage unit correspondsto one bit in precoder buffer 109). Thus accumulated “soft” decisionsafter a certain number of received samples are saved in storage buffer210. As soon as the definite required minimum number of “soft” decisionsis delivered to the storage buffer (determined by iterative decoder 213)corresponding to the data package bits from precoder buffer 109,decoding procedure for the “soft” decisions of the data package receivedfrom precoder buffer 109 starts in iterative decoder 213.

Examples of such procedures are widely known (a similar procedure isdescribed for example, in [3]), and are unrelated to the applicationsubject and therefore are not dwelt upon in detail. It should be notedthat decoding may start in iterative decoder, even when a part of cellsin the storage unit is not filled. At the same time, the code propertieswhile iterative decoding will be equivalent to the similar puncturedcode properties [4, 5], i.e. will be close to optimal.

After each decoding attempt in data integrity checking unit 214,requesting corresponding iteration (rigid decisions) from the iterativedecoder, integrity of the received data package is checked (inaccordance with the provided for by the encoder), using these rigiddecisions. In case the check is successful, the received data package istransferred to the unpacking/restoring unit 215 for unpacking with thecontainer extraction and the information object restoration.Additionally an iteration termination command is formed in the dataintegrity checking unit and conveyed to the iterative decoder. Then theinformation object is transferred through the output of the receivingapparatus to the user device (to the upper processing level).Simultaneously a reception acknowledgement signal may be generated usingthe additional output (Addout) of the receiving device and theacknowledgement signal is sending to the transmission apparatus via anoptional auxiliary (backward) communication channel (for example,through the radio channel, acoustic channel or visual channel) of thereceiving device.

Further data decoding from the storage buffer is carried out with adefinite periodicity provided that during the complete decoding cycle(for example, determined by the several tens of iterations) the datapackage was not restored and a new sample through the firstdemultiplexer (DM1) 207 has arrived (i.e. storage buffer content isrenewed). In the iterative decoder decoding procedure is startedrepeatedly, using the new data from the storage buffer. Such repeateddecoding procedure is performed until the decoder is capable oferror-free restoring of the transmitted data package of precoder buffer109.

The described system has the following features.

First, without application of the backward communication channel thesystem is capable of transferring information object from thetransmitter to the receiver within a minimum time interval providedthere is a certain signal-to-noise ratio in the communication channel.In case of correct choice of the convolution encoder (in CE) andinterleaving algorithm in the repeating/interleaving unit (which areknown and not described in the given application) the encoder, used forinformation object transfer through any communication channel and thetransmission system insures the transmission speed approximatinginformation throughput of the communication channel in the wide range ofsignal-to-noise ratios.

Dependence of the transmission speed on the signal-to-noise ratio isillustrated on FIG. 4. Characteristics of the system are given forcomparing purposes on FIG. 4, using a turbo-code in combination with anideal code with erasure (for example, raptor code [6]). As is seen fromthe diagram comparison on FIG. 4, the traditional system, using theturbo code with the fixed code rate, is provided for a definitesignal-to-noise ratio (in the given example for minus 6 dB) and in thispoint assures the transmission speed approximating informationthroughput of the communication channel. However, in case of an increaseof signal-to-noise ratio, the transmission speed remains unchanged anddiffers considerably from the information throughput of the channel.Also in case of a decrease of the signal-to-noise ratio less than minus6 dB the transmission speed drops drastically, since by suchsignal-to-noise ratios, correcting capacity of the fixed rate turbo-codedoes not allow to achieve reception of the information object with lowerror possibility.

In contrast, the disclosed system, inconsiderably losing out to thesystem with a fixed code in one point (minus 6 dB), enables theachievement of the transmission speed approximating informationthroughput of the channel in a wide range of signal-to-noise ratios. Inthe given example a real transmission system is used taking into accountredundancy, connected with the control channel transmission and anecessity to transfer pilot signals for operation of the channelequalizer in the receiver. Accordingly, actual transmission speed cannot closely approach theoretical information throughput of the channel.Besides, by low signal-to-noise ratios, problems appear connected withsynchronization errors and the errors while control channel reception,affecting the system operation by the very low signal-to-noise ratios(less than minus 8 dB).

As a second feature, due to the application of the adaptive spectrumadjustment of the transmitted signal, the maximum transmitted signalpower is achieved by the minimum acoustic perceptibility and at the sametime preserving wide-band properties of the signal.

Despite of the fact that the invention is shown and described with thereference to its specific variants of the embodiment, specialists in thegiven art must understand that different changes in respect of the formand content can be made without deviating from the essence and thebounds of the invention, defined by the enclosed claims.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. An encoding method comprising the steps of:encoding an input information object according to a first presetencoding scheme; selecting a preset set of bits from the encoded inputinformation object, and outputting the selected preset set of bits as asample; generating a control packet including information on the sampleby encoding according to a second preset encoding scheme; assembling thesample with the control packet; modulating the assembled sample into asound signal according to a preset modulation scheme; and transmittingthe sound signal as an audible tone to an external receiving apparatus,using an acoustic communication channel, wherein the step of generatingthe control packet comprises: generating control data includinginformation related to a size of the input information object and asample number; and generating the control packet by encoding the controldata according to the second preset encoding scheme.
 2. The encodingmethod as claimed in claim 1, further comprising a step of receivinginformation on an exterior sound communication channel and obtaining asound spectrum of the exterior sound communication channel, wherein aspectrum of the sound signal is compensated for when modulation of thesound signal is performed.
 3. The encoding method as claimed in claim 1,further comprising: receiving an exterior audible sound through anexterior microphone and an analog-to-digital converter and analyzing aspectrum configuration and a level of sound noise in a communicationchannel; and calculating an optimal signal spectrum in compliance with apsycho-acoustic model of acoustic perception.
 4. The encoding method asclaimed in claim 3, wherein the step of modulating the assembled sampleinto a sound signal comprises the steps of: correcting a spectrum of theassembled sample according to the calculated optimal signal spectrum;modulating the assembled sample according to the at least one presetmodulation scheme; and adding a synchronous signal to the modulatedsample in a time domain.
 5. The encoding method as claimed in claim 1,wherein the step of encoding the input information object comprises thesteps of: adding a header label to the input information object andperforming a bite set for integrity checking, thereby packing the inputinformation object into a standard container; and receiving the packedinput information object, repeating the received input informationobject a definite number of times in consideration of a size of theinput information object, and interleaving the repeated inputinformation object.
 6. The encoding method as claimed in claim 5,wherein the step of encoding the input information object furthercomprises a step of receiving the repeated and interleaved inputinformation object, and performing a convolution code encoding of therepeated and interleaved input information object.
 7. The encodingmethod as claimed in claim 1, wherein the step of selecting the presetset of bits from the encoded data comprises the steps of: generating asample number for identification of the sample at a preset period; andgenerating a pseudorandom number of addresses in consideration of a sizeof the input information object during generation of the sample number.8. The encoding method as claimed in claim 1, wherein the second presetencoding scheme is carried out by a high redundancy code high noiseimmunity compared to the first preset encoding scheme.
 9. A transmissionapparatus comprising: an encoder; and a speaker connected to an outputof the encoder; wherein the encoder is configured to: encode an inputinformation object according to a first preset encoding scheme; select apreset set of bits from the encoded data and output the selected set ofbits as a sample; generate control data including information related toa size of the information object and a sample number; generate a controlpacket by encoding the control data according to a second presetencoding scheme; assemble the sample with the control packet; modulatethe assembled packet into a sound signal according to at least onepreset modulation scheme; and transmit the sound signal as an audibletone to an external receiving apparatus, using an acoustic communicationchannel.
 10. The transmission apparatus as claimed in claim 9, whereinthe second preset encoding scheme is carried out by a high redundancycode high noise immunity compared to the first preset encoding scheme.11. The transmission apparatus as claimed in claim 9, wherein theencoder comprises: a precoder for encoding the input information objectaccording to the second preset encoding scheme and storing the encodedinformation object in a precoder buffer; a sample number/addressgeneration unit for generating a sample number of each sample and anaddress, which corresponds to each bit of each sample and the address ofthe precoder buffer; a multiplexer for selecting a bit of the precoderbuffer corresponding to the address generated by the samplenumber/address generation module; a sampling buffer for storing a bit ofeach sample output from the multiplexer; a control packet generationmodule for generating the control packet including information on thesample number generated by the sample number/address generation module;a packet assembling unit for assembling the sample stored in thesampling buffer with the control packet generated by the control datageneration module; and a modulation module for modulating the packetoutput from the packet assembling unit into a sound signal according tothe at least one preset modulation scheme.
 12. The transmissionapparatus as claimed in claim 11, wherein the encoder further comprisesa spectrum calculation module for receiving information on an exteriorsound communication channel and obtaining a sound spectrum of thereceived sound communication channel, and wherein the modulation modulecomprises a configuration for compensating for a spectrum of a soundsignal based on information provided by the spectrum calculation module.13. The transmission apparatus as claimed in claim 12, wherein thespectrum calculation module comprises: a communication channel analyzerfor receiving an exterior audible sound through an exterior microphoneand an analog-to-digital converter and analyzing a spectrumconfiguration and a level of sound noise in a communication channel; anda spectrum estimator for receiving an output from the communicationchannel analyzer and calculating an optimal signal spectrum incompliance with a psycho-acoustic model of acoustic perception.
 14. Thetransmission apparatus as claimed in claim 11, wherein the modulationmodule comprises: a spectrum correction unit for correcting a spectrumof a packet output from the packet assembling unit; a modulator formodulating a packet output from the spectrum correction unit accordingto the at least one preset modulation scheme; and a synchronizationsequence addition unit for adding a synchronous signal to an outputsignal of the modulator in the time domain.
 15. The transmissionapparatus as claimed in claim 11, wherein the precoder comprises: acontainer compacting unit for adding a header label to the informationobject and performing a bite set for integrity checking, thereby packingthe information object into a standard container; and arepeating/interleaving unit for receiving output data of the containercompacting unit, repeating the output data a definite number of timesdetermined in consideration of the size of the information object, andinterleaving the repeated data.
 16. The transmission apparatus asclaimed in claim 15, wherein the precoder further comprises aconvolution encoder for receiving data output from therepeating/interleaving unit, performing a convolution code encoding ofthe data, and storing a result of the convolution code encoding in theprecoder buffer.
 17. The transmission apparatus as claimed in claim 11,wherein the sample number/address generation module comprises: a samplenumber generator for generating a sample number for identification of asample at a preset period; and an encoder address generator forgenerating a pseudorandom number of addresses in consideration of thesize of the information object during generation of the sample number.18. The transmission apparatus as claimed in claim 11, wherein thecontrol packet generation module comprises: a control data generationunit for generating the control data; and a control data encoder forgenerating the control packet.